81 Mazda rx7. As the title says its been doing something weird lately, so a few months back (6 maybe more) my car started to have a hard time starting, the egine would fire just fine when i turned the key but as soon as i released the key the car would die, after about the 3rd or 4th try it starts fine and runs. This "symptom" went away and only just reappeared (without me doing anything about it). and now it brought a friend. now when im just driving normally the car will die randomly. This happens mostly when its cold outside (might be coincidence) and not sure if this is related at all but fuel economy dropped as well from around 20 miles to the gallon down to around 15. can someone please help me. I dont know what to look at first. the first thing that comes to mind is fuel pump.

 

You have an electrical problem somewhere in the ignition/starting system. Try swapping the coils (label and take pics before doing this). If it's a bad coil on the leading plugs, this will swap it to the trailing. The car will run without the training.

It could also be the ignition switch itself. If swapping the coils doesn't work, try cleaning the ignition switch with contact cleaner.

It could also be a bad ground. I would think this would also show its face when cranking though.

 

---> OP "the engine would fire just fine when i turned the key but as soon as i released the key the car would die" - - "now when im just driving normally the car will die randomly. This happens mostly when its cold outside."

---> KCREPU "It could also be the ignition switch itself. "

That'd be my first guess; the 'run' contact for the ignition being dirty or pitted and not making good contact, or a loose connection along that circuit path. Cold weather shrinks metal parts; electrical contact problems will often get better or worse as temperature changes.

 

The keyswitch harness would be my first looked at suspect also.
Something else,

I had a bad experience once of taking apart the keyswitch harness assembly. It`s a white round fat thing that plugs into the mechanical housing around the steering column that the ignition key fits into. I wanted to clean the contacts in the harness plug. Had the connector in my hand and was using a screwdriver to pry the lips off of the connector housing. The thing literally exploded in my hand spraying ball-bearings and other parts, all over the garage. THAT was one LONG night finding all of the parts that went everywhere, so I could drive the car to work the next day.

 

i had the same issue, it was the ignition switch. i soldered a high amperage toggle to the ignition switch activate the main circuit.

 

Not cheap, but I had to buy a new switch. Rock Auto was the best price. Took a few minutes to swap. I bet if you take the switch out it will fall apart.

 

Dang that would suck to have an ignition switch fail on ya. I'll be cleaning the contacts on mine now just to be safe!

 

I had one physically lock up on me last winter. Just went out one day and it wouldnt budge no matter what I did. I sprayed seafoam inside the key slot and waited a day, and it broke loose. It was still rough rotation, but I kept spraying deep creep in it and rotating the key and it was back to normal after a couple days.